The retina is the part of the eye that responds to light from an ocular field of view and converts the light to signals to begin image processing. Visual processing continues in the brain where the retinal visual information is integrated spatially, temporally and with ocular movements to achieve visual perception of the ocular field of view. An optical axis is a straight line perpendicular to the front of the eye and extending through a center of the pupil, defined herein as coaxial.